<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>黑客帝国数字流</title>
  <style>
    canvas {
      display: block;
    }
  </style>
</head>

<body>
  <canvas id="c"></canvas>
  <script>
    var c = document.getElementById("c");
    var ctx = c.getContext("2d");

    //making the canvas full screen
    c.height = window.innerHeight;
    c.width = window.innerWidth;

    //chinese characters - taken from the unicode charset
    var txts = "0123456789";
    //converting the string into an array of single characters
    txts = txts.split("");

    var font_size = 16;
    var columns = c.width / font_size; //number of columns for the rain
    //an array of drops - one per column
    var drops = [];
    //x below is the x coordinate
    //1 = y co-ordinate of the drop(same for every drop initially)
    for (var x = 0; x < columns; x++)
      drops[x] = 1;

    //drawing the characters
    function draw() {
      //Black BG for the canvas
      //translucent BG to show trail
      ctx.fillStyle = "rgba(0, 0, 0, 0.05)";
      ctx.fillRect(0, 0, c.width, c.height);

      ctx.fillStyle = "#0F0"; //green text
      ctx.font = font_size + "px arial";
      //looping over drops
      for (var i = 0; i < drops.length; i++) {
        //a random chinese character to print
        var text = txts[Math.floor(Math.random() * txts.length)];
        //x = i*font_size, y = value of drops[i]*font_size
        ctx.fillText(text, i * font_size, drops[i] * font_size);

        //sending the drop back to the top randomly after it has crossed the screen
        //adding a randomness to the reset to make the drops scattered on the Y axis
        if (drops[i] * font_size > c.height || Math.random() > 0.95)
          drops[i] = 0;

        //incrementing Y coordinate
        drops[i]++;
      }
    }

    setInterval(draw, 33);
  </script>
</body>

</html>